@Dmacfarlan
This is a very useful website, and congratulations to the producers. I am carrying out some palaeontological research, mostly on existing collections, This requires dealing with grid references from a variety of maps, and it is often helpful to go back to the original map. the pre-1949 datum Provisional Grid is hard to deal with as the difference in grid is more or less random between sheets. Your proposed 1949 compilation will help this, as does the AU Library compilation